1. Field of the Invention
The present invention is in the field of one-way valves designed to replace diseased venous or arterial valves present in the circulatory system. More specifically, the present invention is directed to the replacement of a diseased valve in the circulatory system through a percutaneous approach.
2. Description of Background Art
The Sigmoid Valves
The mammalian circulation needs the presence of one-way valves to maintain forward blood flow. These valves are found in the outflow of the right and left ventricles (“pulmonary” and “aortic” valves, respectively), and in the large veins. Because of their similar anatomic structure, they are called “sigmoid” or “semilunar” valves. This common structure consists of one, two, or three very thin flaps called “cusps” or “leaflets.” Each flap has a semicircular shape with a curved free edge and a curved base that is inserted into the vessel wall. The insertion of the free edge of the cusp to the vessel wall is called the “commissure.”Immediately downstream to each leaflet, the wall of the vessel has three dilatations or bulges called “sinuses of Valsalva.” There are as many sinuses of Valsalva as leaflets (i.e., a trileaflet valve has three sinuses). These elements of the normal sigmoid have been incorporated in the design of the present invention.
Sigmoid Valve Replacement
In disease, the function of the sigmoid valves is impaired either through narrowing of the valve (“stenosis”) or lack of complete closure, which results in backflow (“regurgitation”). In both circumstances, the whole circulation of the blood and the heart is altered and causes severe symptoms in the patient. Although replacement of the diseased cardiac valves is frequently performed with prostheses, replacement of the venous valves is not done because of the lack of an appropriate prosthesis. According to the material used, heart valve prostheses are classified as mechanical or biologic. Mechanical valves do not resemble the natural sigmoid valves. The biologic prostheses replicate natural anatomy. Tissue valves can be normal sigmoid valves obtained from a cadaver (homograft) or animal (xenograft). Most xenografts are tanned with glutaraldehyde to reduce rejection and increase durability. These hybrids, called “bioprostheses,” are presently the most popular tissue valves. More recently, to improve their hemodynamic performance, tanned animal sigmoid valves have been implanted without a stent (stentless bioprosthesis).
The surgical implantation of heart valve prostheses is a major operation that requires opening the chest and going on cardiopulmonary bypass. The success of percutaneous vascular stenting in coronary and peripheral arteries has encouraged attempts at placing a biologic valve within a large supporting stent so that it can be delivered through a catheter and deployed in the desired position. Recently, two sigmoid valves have been percutaneously implanted in patients. The publications by Bonhoeffer et al. Implantation of a Bovine Valve in Pulmonary Position: A Lamb Study. Circulation 2000; 102:813-816 and Bonhoeffer et al. Percutaneous replacement of pulmonary valve in a right-ventricle to pulmonary-artery prosthetic conduit with valve dysfunction. Lancet 2000; 356:1403-1405 describe successful percutaneous implantation of a glutaraldehyde-treated bovine jugular valve placed within a stent and deployed inside a previously implanted valved conduit in the pulmonary position. The publication by Cribier et al. Percutaneous Transcatheter Implantation of an Aortic Valve Prosthesis for Calcific Aortic Stenosis. First Human Case Description. Circulation 2002; 106:3006-3008 describes aortic valve replacement with a valve made of three bovine pericardial leaflets mounted within a tubular, slotted, stainless steel balloon-expandable stent.